ViewModel + LiveData + Kotlin Coroutines

KotlinCoroutinesMVVM.kt

class MainActivity : AppCompatActivity() {

    val mainViewModel: MainViewModel by lazy {
        ViewModelProviders.of(this).get(MainViewModel::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mainViewModel.getUsr()
        mainViewModel.addUser.observe(this, Observer {
            when (it) {
                is PushResult.Success -> text.text = "OK"
                is PushResult.Error -> Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show()
            }
        })
        mainViewModel.updateUser.observe(this, Observer {
            when (it) {
                is PullResult.Success -> text.text = "OK2"
                is PullResult.Error -> Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show()
            }
        })
    }

    fun onClick() {
        mainViewModel.addUser(mapOf("name" to "Nobita"))
    }
}


class MainViewModel(val userRep: UserRepository) : ViewModel() {
    val addUser = MutableLiveData<PushResult>()
    val updateUser = MutableLiveData<PullResult>()
    fun addUser(user: Map<String, Any>) {
        viewModelScope.launch(IO) {
            addUser.postValue(userRep.push(user))
        }
    }

    fun getUsr() {
        viewModelScope.launch(IO) {
            updateUser.postValue(userRep.pull())
        }
    }
}

class UserRepository(val db: FirebaseFirestore) {
    // FIXME Map<String, Any> to User class
    suspend fun push(user: Map<String, Any>): PushResult {
        return suspendCoroutine { continuation ->
            db.collection("users")
                .add(user)
                .addOnCompleteListener {
                    when (it.isSuccessful) {
                        true -> continuation.resume(
                            PushResult.Success(
                                checkNotNull(it.result)
                            )
                        )
                        false -> continuation.resume(
                            PushResult.Error(
                                checkNotNull(it.exception)
                            )
                        )
                    }
                }
        }
    }

    suspend fun pull(): PullResult {
        return suspendCoroutine { continuation ->
            db.collection("users")
                .get()
                .addOnCompleteListener {
                    when (it.isSuccessful) {
                        true -> continuation.resume(
                            PullResult.Success(
                                checkNotNull(it.result)
                            )
                        )
                        false -> continuation.resume(
                            PullResult.Error(
                                checkNotNull(it.exception)
                            )
                        )
                    }
                }
        }
    }
}

sealed class PushResult {
    data class Success(val id: DocumentReference) : PushResult()
    data class Error(val e: Throwable) : PushResult()
}

sealed class PullResult {
    data class Success(val id: QuerySnapshot) : PullResult()
    data class Error(val e: Throwable) : PullResult()
}

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "your.app.pkg"
        minSdkVersion 23
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.appcompat:appcompat:1.1.0-alpha03'
    implementation 'androidx.core:core-ktx:1.1.0-alpha05'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0-alpha03'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.1.0-alpha03'

// async// kotlin coroutines
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.1.1"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.1.1"
    implementation 'io.reactivex.rxjava2:rxkotlin:2.3.0'

    // firestore
    implementation 'com.google.firebase:firebase-firestore:18.2.0'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.2-alpha02'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0-alpha02'
}